The tricarboxylic acid (TCA) cycle is a system of enzymes in the mitochondrial matrix arranged in a cyclic metabolic structure, including dehydrogenases that converge in the NADH pool and succinate dehydrogenase (on the inner side of the inner mt-membrane) for entry into the membrane-bound ET pathway mET pathway. Citrate synthase is a marker enzyme of the TCA cycle, at the gateway into the cycle from pyruvate via acetyl-CoA. It is thus the major module of the Electron transfer pathway, upstream of the inner Membrane-bound ET pathway (mET-pathway) and downstream of the outer mt-membrane. Sections of TCA cycle are required for fatty acid oxidation (FAO, β-oxidation). Anaplerotic reactions fuel the TCA cycle with other intermediary metabolites. In the cell, the TCA cycle serves also biosynthetic functions by metabolite export from the matrix into the cytosol.
Abbreviation: TCA cycle
Reference: Gnaiger 2020 BEC MitoPathways